1. Field of the Invention
The present invention relates in general to electrochemical devices, and, more particularly, a high power electrochemical device capable of providing instantaneously available high power. For example, such high power devices are useful for providing instantaneous power in the event of transient power losses and poor power quality of supplied main power.
2. Prior Art
The need for quality power is ever increasing. Current and future sophisticated electric and electronic devices are particularly sensitive to power supply issues. For example, poor power supply and transient power losses in supplied main power which last only milliseconds can have an adverse impact on electronic equipment. Such power issues can result in the destruction of electronic equipment, the loss of generated data, the loss of communication with other equipment, and the loss of time required to reset and restart procedures that were interrupted by the loss in power.
Certain solutions have been developed to provide instantaneous power in response to transient power interruptions and other associated power problems, including, uninterruptible power systems (UPS systems). In such systems, lead-acid batteries are often used to provide temporary power when necessary. While such solutions have had some success, lead-acid batteries have certain problems, including, but not limited to, a limited cycle life, a high failure rate, high cost of maintenance, weight and size considerations, poor durability, self discharge issues, sensitivity to deep discharge and to temperature, as well as toxicity.
The present invention is directed to an electrochemical energy storage device, such as a rechargeable battery device, wherein both the cathode and anode are constructed from high rate materials, so as to result in high current density discharge capability of at least 0.05 A/cm2. Such battery devices are of great interest for applications such as power quality, power backup or hybrid electric vehicles. While such devices exist in the older battery technologies of lead-acid, nickel-cadmium and nickel-metal hydride, large high power Li-ion batteries have not been introduced in large quantities to the market place yet, mainly due to safety considerations. Therefore, it is an object of this invention to disclose a Li-ion battery device with excellent safety and performance characteristics by choosing materials and design geometries to minimize resistive losses and to maximize safety performance under abuse conditions, e.g. under full short-circuit. This document will disclose that a battery according to the present invention is safe under short-circuit conditions even in the absence of any safety features such as fuses, current limiters or temperature-activated switching devices. The present document will further disclose how to maximize power densities to at least 1000 W/kg, despite the stringent safety requirements.
Other solutions are electro-mechanical energy storage devices, such as both low speed and high-speed flywheels. Such devices draw energy from a primary power source and store it as the kinetic energy of the flywheel. When the primary power source is interrupted, the energy stored in the kinetic energy of the flywheel is converted into electrical energy. While this solution has likewise provided some success, there have been problems. These problems include limited energy storage available in a flywheel, load management abilities, excessive energy losses, safety concerns, high material costs and limited life of parts such as bearings or vacuum pumps.
Of particular interest in the power-supply area are electrochemical devices for high-power applications. These devices are capable of storing large amounts of energy through chemical reactions, and then are able to release that energy when needed. A number of different device types have been explored in this area, including the above-mentioned lead-acid batteries or other electrochemical energy storage devices such as nickel-cadmium, nickel metal hydride, zinc bromine batteries or supercapacitors. None of these devices are satisfactory for certain applications in the power quality sector, either due to their limited power or energy content for a given foot print or volume, their limited product life at more elevated temperatures, their sloping discharge profile, their toxicity or a combination of these disadvantages.
Accordingly, it is an object of the present invention to provide instantaneous power in response to interruptions and other power problems without the above-identified drawbacks.
These and other objectives will become apparent in light of the specification and claims appended thereto.